1. Field of the Invention
The present invention relates generally to magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval. More particularly, the present invention relates to enhanced magnetoresistive (MR) resistivity sensitivity giant magnetoresistive (GMR) sensor elements employed within magnetic data storage and retrieval.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive M(R) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, magnetoresistive (MR) sensor elements whose operation is predicated upon a giant magnetoresistive (GMR) effect are presently of considerable interest insofar as those magnetoresistive (MR) sensor elements typically exhibit enhanced levels of magnetoresistive (MR) resistivity sensitivity in comparison with magnetoresistive (MR) sensor elements whose operation is predicated upon magnetoresistive (MR) effects other than the giant magnetoresistive (GMR) effect. The giant magnetoresistive (GMR) effect is understood by a person skilled in the art to be exhibited by a magnetoresistive (MR) sensor element fabricated employing a series of ferromagnetic layers having interposed therebetween a series of non-magnetic conductor spacer layers, where the thicknesses of each non-magnetic conductor spacer layer within the series of non-magnetic conductor spacer layers is chosen such that adjacent ferromagnetic layers within the series of ferromagnetic layers are magnetically coupled and biased anti-parallel.
For purposes of clarity, within the context of the present invention, magnetoresistive (MR) resistivity sensitivity is intended as a measure of proportion of resistance change normalized to an absolute resistance of a magnetoresistive (MR) sensor element (i.e. dR/R) when measuring a magnetic signal within a magnetic data storage medium while employing the magnetoresistive (MR) sensor element. The magnetoresistive (MR) resistivity sensitivity of a magnetoresistive (MR) sensor element is alternatively known as the magnetoresistive (MR) coefficient of the magnetoresistive (MR) sensor element. Magnetoresistive (MR) sensor elements exhibiting enhanced magnetoresistive (MR) resistivity sensitivity are desirable within the art of magnetoresistive (MR) sensor element fabrication since such enhanced magnetoresistive (MR) resistivity sensitivity clearly inherently allows for detection within a magnetic data storage medium of weaker magnetic signals with increased linear density and thus also inherently allows for an increased areal density of the magnetic data storage medium within a magnetic data storage enclosure which employs the magnetoresistive (MR) sensor element which exhibits the enhanced magnetoresistive (MR) resistivity sensitivity.
A typical commercial embodiment of a magnetoresistive (MR) sensor element whose operation is predicated upon the giant magnetoresistive (GMR) effect is a spin valve magnetoresistive (SVMR) sensor element. Spin valve magnetoresistive (SVMR) sensor elements typically employ a pair of ferromagnetic layers separated by a non-magnetic conductor spacer layer, where one ferromagnetic layer within the pair of ferromagnetic layers is additionally magnetically pinned through contact with a hard magnetic material layer to provide a fixed magnetization angle between a first magnetization direction within the magnetically pinned ferromagnetic layer and a second magnetization direction within the other ferromagnetic layer which is un-pinned. The un-pinned other ferromagnetic layer is alternatively referred to as a free ferromagnetic layer. The giant magnetoresistive (GMR) effect within a spin valve magnetoresistive (SVMR) sensor element is predicated upon differential electron scattering trajectories within the spin valve magnetoresistive (SVMR) sensor element incident to magnetic data recording media biasing of a free ferromagnetic layer with respect to a magnetically pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element.
It is thus towards the goal of forming for use within magnetic data storage and retrieval giant magnetoresistive (GMR) sensor elements, such as but not limited to spin valve magnetoresistive (SVMR) sensor elements, while forming the giant magnetoresistive (GMR) sensor elements to exhibit enhanced magnetoresistive (MR) resistivity sensitivity, that the present invention is directed.
Various magnetic sensor elements, including but not limited to giant magnetoresistive (GMR) sensor elements, which possess desirable properties have been disclosed within the art of magnetic sensor element fabrication, including but not limited to giant magnetoresistive (GMR) sensor element fabrication.
For example, Goubau et al., in U.S. Pat. No. 5,268,806, disclose a magnetoresistive (MR) sensor element having a conductor lead structure which remains stable not only during processing when fabricating the magnetoresistive (MR) sensor element, but also over the useful operational life of the magnetoresistive (MR) sensor element. The magnetoresistive (MR) sensor element employs a conductor lead structure comprising: (1) a seed layer contacting a magnetoresistive (MR) layer within the magnetoresistive (MR) sensor element, where the seed layer is formed from a material selected from the group consisting of chromium, tungsten, an alloy of titanium and tungsten, and an alloy of tantalum and tungsten, and where the seed layer has a body centered cubic lattice structure; and (2) a conductor layer formed upon the seed layer, where the conductor layer is formed of tantalum and where the conductor layer also has a body centered cubic lattice structure.
In addition, Fontana Jr. et al., in U.S. Pat. No. 5,701,223, disclose a spin valve magnetoresistive (SVMR) sensor element with improved magnetoresistive (MR) properties, such as an enhanced magnetoresistive (MR) resistivity sensitivity, as well as improved chemical properties, such as an enhanced corrosion resistance of an antiferromagnetic pinning material layer within the spin valve magnetoresistive (SVMR) sensor element. The spin valve magnetoresistive (SVMR) sensor element realizes the foregoing objects by employing when forming the spin valve magnetoresistive (SVMR) sensor element: (1) a pair of anti-parallel antiferromagnetically biased ferromagnetic material layers separated by a non-magnetic conductor spacer layer as a composite pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element, in conjunction with; (2) a pinning material layer formed of a pinning material selected from the group consisting of nickel oxide, nickel-cobalt alloy oxides and iron-manganese-chromium alloys.
Further, Lee et al., in U.S. Pat. No. 5,731,936, disclose an anisotropic magnetoresistive (MR) sensor element, such as a soft adjacent layer (SAL) magnetoresistive (MR) sensor element, with an enhanced magnetoresistive (MR) resistivity sensitivity as well as an enhanced thermal stability. The anisotropic magnetoresistive (MR) sensor element employs a nickel-iron-chromium alloy or a nickel-chromium alloy spacer layer adjoining a nickel-iron alloy magnetoresistive (MR) layer formed within the anisotropic magnetoresistive (MR) sensor element.
Still further, Chang et al., in U.S. Pat. No. 5,763,108, disclose a high saturation magnetization magnetic material for use when fabricating a magnetic head, and a magnetic head fabricated employing the high saturation magnetization magnetic material for use when fabricating the magnetic head. The high saturation magnetization magnetic material has an elemental composition comprising about 40 to about 60 weight percent iron, about 40 to about 60 weight percent nickel and about 0.002 to about 1 percent tin.
Finally, Lin, in U.S. Pat. No. 5,768,071, discloses a spin valve magnetoresistive (SVMR) sensor element having an improved magnetic stability of a pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element. The spin valve magnetoresistive (SVMR) sensor element realizes the foregoing object by employing when forming the spin valve magnetoresistive (SVMR) sensor element a discontinuous nonmagnetic interlayer interposed between an antiferromagnetic pinning material layer and the pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element.
Desirable in the art of giant magnetoresistive (GMR) sensor element fabrication are additional methods and materials which may be employed for forming with enhanced magnetoresistive (MR) resistivity sensitivity giant magnetoresistive (MR) sensor elements, including in particular spin valve magnetoresistive (SVMR) sensor elements.
It is towards the foregoing object that the present invention is directed.